Dynamo electric machinery



Feb. 27, 1940. D. 0. sPRouLE DYNAMO ELECTRIC MACHINERY 2 Sheets-Sheet 1NVENTofd Filed March 2l, 1939 I Domani Orr SPYOUIQ bwa@ L 41A AT1-y,

D. O. SPROULE DYNAMO ELECTRIC MACHINERY Feb. 27, 1940.r

Filed March 21, 1939 2 SheetSf-SheefZ Dafmld Orr Sp'yo'ble.

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Patented Feb. 27, 194() UNITED STATES 2,191,309 nYNAMo Emic'rnrcMACHINERY Donald Orr Sproule, London, England, assignor oi' one-third toArthur Joseph Hughes, Essex. England, and one-third to Henry Hughes &Son Limited, London, England, a British limited liability companyApplication March 21, 1939, Serial No. 263,153 In Great Britain March16, 1938 5 Claims.` (Cl. 17h-209) This invention relates to improvementsin dynamo electric machinery and has for its object to provide meanswhereby the efficiency of impulse generators can be increased, the riskI damage to contacts in associated inductive circuits be reduced and thesharpness of cut-oil! of each individual pulse be accentuated in asimple and inexpensive manner.

The generation of powerful electrical pulses of short time duration inthe output circuit' of a generator, the rotor of which has been allowedto acquire momentum and has extracted electrical energy from a supplysource for a compara- 4 tively greater period of time and stored it askinetic energy is known; in some cases the output -circuit has beenconnected momentarily to the generator and in other cases the fieldcircuit has been energised momentarily thus eliminating iron losses inthe absence of output but introduc-v ing difficulties with contacts dueto the voltage surge consequent upon the breaking of the field circuit.

This invention consists in an improved electrical impulse generator andis characterised in that the iield of the generator is alternatelymaginetised by a periodically interrupted direct current anddemagnetised by an alternating current pulse which is substituted forthe direct vcurrent when the voltages of the two currents aresubstantially identical, the flow of said alternating current beinginterrupted when the current in the field winding is zero.

Further the invention is characterised in that on the'interruption ofthe supply of direct current to the field of the generator the energy in-said iield and in the field of associated devices in the output circuitof the generator is neutralised by the demagnetising effect of analternating current applied to the eld winding. 40 In the drawings:

Figure 1 is a diagram showing one arrangement of the circuitsand'switchcs of an impulse generator according to this invention.

.Figure 2 is a diagram showing by way of exof the various switches.

Figure 3 is a diagram showing the changes in voltage across thegenerator field winding with 59 the switches arranged according toFigure 2,v Figure 4 is a diagram showing the ileld voltage change inFigure 3 drawn tol a larger sca1e,'

Figure 5 is a diagram companionwith Figure 3 and showing the outputvoltage of the genera- 55 tor, and

ample la sequence and time periods of operation Figure 6`is a diagramshowing the pulse of Figure 5 drawn to a larger scale.

In Figure 1 a diagrammatically represents a shunt wound direct currentelectromotcr and b an alternating current generator. 5

The electromotcr a comprises a field magnet winding c, an armaturewinding d, a commutator e and brushes f, f' whilst the generator bcomprises a field winding g, an inductive winding h, and slip rings yand k cooperatingwithl0 brushes l and m respectively.

The windings d and h the commutator e and slip rings y' and k aremounted on a spindle n which also is provided with slip rings p and qcooperating with brushes 1.' and s respectively and 15 with a worm o.

The worm o engages a '.worm wheel o1 mounted on a shaft t carrying fourswitch cams u, v,

w and and a worm y which engages a worm` wheel y1 carrying a switch came. 20

The positive I and negative 2 of the direct current mains respectivelyare connected by the conductors 3 and 4 to the brushes f, f and to thewinding c in shunt therewith in the usual way, the positive I also beingconnected by the con- 25 ductor 5 to the contact blade II operated bythe cam u whilst the negative 2 also is connected by the conductor 6 tothe contact blade 2| operated by the cam v. t

Diametrically opposite points in the armature 30 winding d are connectedby the conductors 'I and 8 to the slip rings p and q respectively andthe brush r is connected by the conductor 9 to the contact blade r1operated .by the cam w whilst the brush s is connected by the conductor`III to 35 the contact blade s1.

A contact g1 is arranged between the contact blades II and r1 and isconnected by the conductor I2 to one end ofthe field winding g the otherend of which is connected by the conductor I3 to 41) the contact blade aadapted to cooperate with the contact blade g3 operated by the cam e,said blade g3 being connected by the conductor I4 to the contact c*arranged between the contact blades 2l and s1. 45

'Ihe direct current, beside energising the motor a to rotate theY shaftVn and .the parts p, q, o, h, j and k mountedy thereon, flows fromthepositive I of the mains through the conductor 5 to the contact blade IIand from thence,- when raisedby the cam u, to. the contact blade g1through theconductor I2, field winding g and conductor I3 to the contactblade g2, contact being efrected with the .blade g3, when raised by thecam z. to complete the circuit through the con- '55 ductor Il, thecontact blade g4, the contact blade 2I (when raised by the cam v) andthe conductor E to the negative 2 of the mains.

The slip rings p and q being connected to diametrically opposite pointsof the armature winding d will have applied thereto an alternatingvoltage of a maximum potential'equal to the potential ofthe directcurrent. This alternat ing current will pass from the brush r throughthe conductor 9 to the contact blade r1 and through the contact bladeg1, when the blade r1 is allowed to fall by the cam w, the conductor |2,the winding g and the conductor I3 to the contact blade g2, thencethrough the contact blade g3, when it is raised by the cam z, theconductor I4, the contact blade g4, the contact blade s1, when it isallowed to fall by the cam x, and the conductor I0 to the brush s.

The cams u, v, w, a: are so shaped and timed relatively to one anotherthat during the formation of an impulse the cams u and v raise theblades II and 2i until they contact with the blades g1 and g4respectively, thus connecting the Winding g to the mains I and 2, if theblades g and g3 are in contact.

The cams w and are so set in relation to the rotation of the slip ringsp and q that the said cams allow the blades r1 and s1 to fall andcontact with the blades g1 and g4 when the voltage at the brushes r ands is at its maximum, i. e., equal to the mains voltage; instantaneouslythe blades II, g1 and r1 are in contact with one another but as theblades are all at the same potential no burning or arcingtakes place,which condition also applies to the blades 2i, g4 and s1 which are incontact with one another at the same time.

After a brief space of time the cams u and u allow the blades Il and 2Ito break contact with the blades g1 and y* but the contact between theblades g1 and r1 and between the blades g4 and s1 is maintained untilthe potential applied to the brushes 1 and s has been reversed asuiiiciently long time to reduce the-current in the winding g to zero,thus producing the voltage change in this winding as shown in Figure 4.

From Figure 3 it will be seen that the voltage changes are separated byperiods of no voltage, the spacing being effected by the cam z andcontact blades q3 and g.

Any kind of gearing may be used to obtain the required velocity ratioand the invention is not limited to worm gearing as shown in Figure 1.

When the output from the generator is to be applied to a sound emittersuch as E in Figure 1 having a field inductance of about .011 henry, theinductance of the field winding g in parallel therewith is about .018henry and the mains voltage is about 24, it is found to be possible todeliver about 440 watts to the transmitter E for about one-fiftieth partof a second with an average input of about 118 watts from the directcurrent mains to the motor a rotating at about 10,000 revolutions perminute.

Figure 2 shows the sequence of operation of the switches, the contactperiods being indicated by hatched areas and as this figure iscoordinated with Figure 3 the formation of the voltage pulses isdisplayed clearly.

In Figure 2 the top group of three lines represents the triple bladeswitch operated by Athe cams u and w, the next group of three' linesrepresent the triple blade switch operated by the cam v and and thelower group oi' two lines represent the switch operated by the cam z.

To facilitate the understanding of the example described, the use of atime scale has been avoided in the drawings, the important time periodshaving been applied to Figures 2 and 4. As-shown about 167 pulses aregenerated in each second,the velocity ratio of the worm o and wheel o1being 33:1 and the velocity ratio of the worm y and wheel y1 being 5:1.

Figure 5 is coordinated with Figures 2 and and indicates the voltageoutput pictorially as the periodicity is about 1,500 per second whichcannot be shown to scale.

The purpose ofthe switch g2 g3 is more or less evident from thedescription inasmuch as it will be seen that by its use it is possibleto secure relatively long periods between the pulses even when the shaftn rotates at a comparatively high speed thus reducing the precisionrequired during the machining and the setting of the cams u, c, w andce, but obviously this switch is unnecessary in some cases and may beomitted.

I claim:

1. An electrical impulse generator comprising a revoluble inductivewinding, means to revolve said inductive winding, means to derive fromsaid inductive winding current impulses generated therein, a fieldwinding, a circuit for said field winding, a source of direct current, asource of alternating current of a maximum potential equal to thepotential of said direct current, first switch'means for connecting saidsource of direct current to said iield winding circuit, second switchmeans for connecting said source of alternating current to said fieldwinding circuit, and control mechanism coupled to said driving means forperiodically actuating said first and second switch means in apredetermined rhythm so as to first close said first switch meansthereby magnetizing said field winding, then after a predeterminedinterval close said second switch means at the moment when thealternating cur rent is at its maximum while the iirst switch means isstill closed, then open said iirst switch means, and finally open saidsecond switch means when the alternating current is at zero and thefield winding has become demagnetized.

2. An electrical impulse generator comprising a revoluble conductivewinding, means to revolve said inductive winding including a directcurrent electromotor having an armature winding, means to derive fromsaid inductive winding current impulses generated therein, a fieldwinding associated with said inductive winding, a circuit for said fieldwinding, a source of direct current connected to said motor to supplyenergy thereto, means for obtaining from the armature winding of saidmotor an alternating current of a maximum potential equal to thepotential of said direct current, rstswitch means for connecting saidsource of direct current to Asaid field winding circuit, second switchmeans for connecting said means for obtaining alternating current tosaid eld winding circuit,r and control mechanism mechanically coupledtol said electromotor for periodically actuating said first and secondswitch means in a predetermined rhythm so as to first close said firstswitch means thereby magnetizing said field winding, then after apredetermined interval close said second switch means at the moment whenthe alternating current is at its maximum while the iirst switch meansis still closed, then open said first switch means, and finally opensaid second switch means when vthe alternating current is at zero andthe field winding has become demagnetized.

3. An electrical impulse generator, as claimed in claim 2, in which saidcontrol mechanism for said switch means comprises a cam shaft driven'electrically connected to diametrically opposite points of the latter,and brushes resiliently pressed against said slip rings to collect thealternating current applied to the latter.

5. An electrical impulse generator, as claimed 5 in claim 2, comprisingan auxiliary switch in said field winding circuit, and means driven bysaid electromotor to close said switch at predetermined intervals.

DONALD ORR SPROULE. 10

